install_osx: try removing sudo from brew commands

[scpeters]

The osx CI is failing in #1424 complaining about running as root:

Error: Running Homebrew as root is extremely dangerous and no longer supported.
As Homebrew does not drop privileges on installation you would be giving all
build scripts full access to your system.

So I've removed the sudo calls from the install_osx script and CI is now passing.

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Before creating a pull request

• Document new methods and classes
• Format new code files using clang-format

Before merging a pull request

• Set version target by selecting a milestone on the right side
• Summarize this change in CHANGELOG.md
• Add unit test(s) for this change

[codecov]

Codecov Report

Merging #1426 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1426      +/-   ##
==========================================
- Coverage      58%   57.99%   -0.02%     
==========================================
  Files         412      412              
  Lines       29794    29794              
==========================================
- Hits        17283    17280       -3     
- Misses      12511    12514       +3

Impacted Files	Coverage Δ
dart/dynamics/Skeleton.cpp	66.16% <0%> (-0.17%)	⬇️